This invention relates to an aqueous, foam-retarding printing ink composition and to a method of using the composition in the manufacture of chemically embossed resinous sheet materials.
Sheets of resinous material have found widespread use as decorative and wear resistant coverings in a wide variety of products. The sheets are used extensively as floor and wall coverings. In many instances, the sheets are made by applying a resinous composition to a backing material, such as felt, paper, woven fabric or the like. The backing material provides strength and serviceability to the sheet.
The resinous sheet materials can include a resilient, cellular foam layer, which is typically formed from a resinous composition containing a foaming or blowing agent that causes the composition to expand on heating. It is known in the art that foamable, resinous sheet materials can be embossed by controlling the decomposition temperature of a catalyzed blowing or foaming agent in the heat-expandable composition. For example, by applying to the heat-expandable composition a reactive chemical compound, which is referred to in the art as a "regulator", "inhibitor", or "retarder", it is possible to modify the decomposition temperature of the catalyzed foaming or blowing agent in the area of application of the reactive compound It is thus possible to produce sheet materials having surface areas that are either depressesd or raised proximate the area of inhibitor application.
The inhibitor is conveniently incorporated in a foam-retarding, printing ink composition, which is printed over the heat-expandable resinous composition. Foam-retarding, printing ink compositions are well known. These compositions are generally based on an organic solvent carrier or vehicle system. While compositions of this type have achieved a certain degree of success, recent State and Federal EPA emission standards for volatile organic solvents (VOS) have made continued use of these compositions costly on an industrial scale. The organic solvents liberated from the compositions must either be recovered or incinerated. In either case, costly equipment and maintenance procedures are required.
In order to meet VOS emission standards, the use of aqueous-alcoholic retarder ink compositions has been proposed. While the aqueous-alcoholic printing ink compositions pose fewer emission problems, it has been reported that the pH of the compositions must be controlled in the alkaline range, and the use of ammoniacal pH regulating agents has been proposed for this purpose. Specifically, it has been proposed to use benzotriazole as a foam growth controlling agent in a aqueous-alcoholic printing ink having a pH in the range of from 8 to 12. Ammonia or other alkaline materials are used to prevent the pH from dropping below a value of about 8. See U.S. Pat. Nos. 4,191,581 and 4,083,907 to Hamilton and 4,407,882 to Hauser et al.
Aliphatic or aromatic dicarboxylic acids and their anhydrides or halides have also been suggested for use as foam inhibitors in printing ink compositions. It has been reported, however, that these inhibitors are not suitable for aqueous printing inks. See U.S. Pat. No. 4,407,882 to Hauser et al.
The use of certain organic carboxylic acids as foam inhibitors has been suggested in U.S. Pat. Nos. 4,369,065 and 4,421,561 to Brixius. The acid must be neutralized, and the foam-growth-controlling ink composition in which the neutralization product is used must have a pH between about 8 and about 12.
There exists a need in the art for an aqueous foam-retarding printing ink composition that can meet State and Federal EPA emission standards for volatile organic solvents without the need for expensive solvent recovery or incineration equipment. There also exists a need for such a composition that will provide an improved environment for workers by eliminating most organic solvent vapors and ammoniacal pH regulating and buffering agents. The composition should provide a safer work environment by reducing the possibility of combustion and fire. The composition should be adaptable for use with conventional printing equipment.